1. Technical Field
The present disclosure relates to remote afterloading devices used to position radioactive treatment source wires inside patients afflicted with cancer or other diseases, and more particularly to a system and method for delivering a medical treatment to a treatment site of such patients.
2. Background of Related Art
Radiation is used to treat cancer and other diseases of the body. Brachytherapy, is a general term for the radiation treatment of cancer at close distances inside the body. During brachytherapy, a radioactive source or sources are positioned in the area needing treatment. Depending on the type of therapy, the radioactive sources are placed permanently inside the body during surgery, or transport tubes (treatment catheters) are placed in the body which are later temporarily loaded with radioactive sources. This temporary afterloading of radioactive material either involves a human handling the radioactive material and receiving radiation exposure, or a machine called a xe2x80x9cremote afterloaderxe2x80x9d that will load and unload the radioactive material into and from the transport tubes. Such remote afterloaders are operated by an individual from a remote location so that the individual will not receive any radiation exposure.
Existing remote a afterloaders are generally used in the cancer field to accurately advance and retract a flexible drive member containing a radioactive source over a specified distance for a specified time period. A remote afterloader generally consists of a flexible simulation drive member, a flexible drive member containing a radioactive element, controllers and drive mechanisms to operate both types of flexible members, a shielding safe for the radioactive element, an internal timer, and an exit port attached to a rotating wheel that allows multiple transport tubes (previously placed into the patient) to be attached to device at the same time.
It is known to use a simulation member for checking the patency of the transport tube without subjecting the patient to undue radiation exposure. After the patency is confirmed, the afterloader sends out the radioactive source. Upon completion of treatment in a first transport tube, the afterloader retracts the source into the shielding safe inside the afterloader, a wheel turns and aligns a slot containing a second transport tube to an exit port. The remote afterloader then repeats its function sending and retracting the simulation member and radioactive source through this second tube. The procedure is repeated until the function is carried out through all the specified transport tubes. Existing remote afterloaders use a fixed, short length radioactive source and multi-step this source many times inside each transport tube to cover the diseased area.
Currently available remote afterloaders require the following complicated procedures before any treatment can take place:
Initially, by hand, physical measurements must be made of each transport tube after it has been positioned inside the body using a simulation member, fluoroscopy, and a calibrated ruler. These measurements must accurately relate the physical distance the radioactive source needs to travel from the distal end of each tube to the inside of each transport tube to treat the disease inside the body.
Secondly, two 90 degree X-Rays showing all the transport tubes inside the body must be made and digitized into a treatment planning computer. The physical measurements taken prior to the X-rays, must be matched up with each digitized transport tube in the treatment planning computer and the physical length measurements along with other treatment data must be entered for each transport tube.
The computer then compiles all the data and a treatment plan is formed and stored on a magnetic computer disk. This computer disk containing the treatment plan is then entered into a treatment computer that programs and operates the remote after-loader. Finally, the treatment takes place.
In most cases, the above setup steps take thirty minutes or more. Existing remote afterloaders were primarily designed for the treatment of cancer but can be used in other treatments of diseases. There are critical factors that will not allow the previously available remote afterloaders to be used in the treatment of certain types of diseases. One main limiting factor is the long setup time required for treatment. In treatments where time is of the essence, such as in the treatment of heart patients, a long setup time could be unacceptable. The present disclosure allows a specially designed remote afterloader to perform its duty in a much shorter time period, eliminating many of the time consuming steps.
Other limiting factors of previous treatment afterloaders are the physical size and amount of equipment necessary to operate a remote afterloader. In many treatment facilities there is not enough room for the amount and size of equipment. Lack of certain safety features (for example, an indirect but not a direct transport tube sensing device to ensure that the transport tube is properly connected to the afterloader, human error when measuring and translating treatment distance, no control of the speed in which the drive members move, no means to fine tune the position of the drive members once they reach their target area) along with the lack of other safety features make the previously available remote afterloaders limited in use and effectiveness.
Various techniques have been developed to treat many different conduits in the body when these conduits have become reduced in size due to the existence of a stenosis or have been completely occluded. These techniques include introducing a deflated balloon catheter to the site of an occlusion or constriction, such as a stenosis, inflating the balloon one or more times to reduce the size of the stenosis, deflating the balloon and then removing the balloon catheter from the treatment site.
With respect to the vascular pathways, angioplasty is used to open an artery or blood vessel in the region where the stenosis or the occlusion has occurred. A typical angioplasty procedure consists of making a small incision through the body and into a blood vessel and then maneuvering a guide wire through the vascular system to a point beyond the stenosis or occlusion. A hollow catheter with a declarable balloon near its distal end is threaded over the guide wire and advanced to the point of stenosis or occlusion. The balloon is then inflated and deflated several times to widen the constricted area, and is then withdrawn from the body.
Unfortunately, although the angioplasty procedure does markedly reduce the area of stenosis or occlusion, many patients exhibit a reoccurrence of the stenosis within a few months of the original procedure.
Although the original stenosis occurs by means of the build up of plaque over a relatively long period of time, experimentation has led many to believe that the reoccurrence of the stenosis after the original angioplasty procedure is unrelated to the cause of the original stenosis. It is believed that the inflation of the balloon catheter used in the angioplasty procedure or the placement of a sent in the area of the stenosis causes irritation to the blood vessel. This irritation produces a mechanism of action called hyperplasia, inducing the inner layer of the blood vessel cells to rapidly reproduce, thereby causing restenosis. It has been proposed that if the blood vessel is irradiated at the point of the stenosis with a radioactive dose, the mechanism that causes hyperplasia would be destroyed without harming the blood vessel itself.
During this procedure, it is important to precisely control the amount of radiation which is directed to the blood vessel wall, since too much radiation could actually induce hyperplasia as well as destroying a portion of the blood vessel, making it possible for an aneurism or rupture to occur.
U.S. Pat. No. 5,213,561 issued to Weinstein et al and U.S. Pat. No. 5,199,939 issued to Dake et al, as well as PCT Application PCT/US92/07447 to Shefer et al, describe various methods and apparatus for introducing radiation to the site of a stenosis to endeavor to prevent rustiness.
The Weinstein et al patent describes a method and apparatus for preventing rustiness after angioplasty. A balloon catheter transported by a conventional guide wire is delivered to the location of the stenosis. Particles or crystals of radioactive material are embedded or mounted on a tube provided inside the balloon catheter. A retractable radiation shielding sleeve is slidable along the tube to cover the source of radioactive material. Upon completion of the angioplasty, the shielding sleeve is retracted and the area of the stenosis is irradiated. Although this apparatus does introduce radiation to the point of the stenosis, the retractable shielding surrounding the source of radioactive material makes this catheter bulky and unwieldy to use. In this regard, it is very doubtful that a catheter system this bulky would fit into the smaller branches or vessels of the heart. It is also doubtful that a catheter this bulky and stiff could be maneuvered through the tighter bends and turns in many of the vessels.
An additional embodiment of the Weinstein et al. patent illustrates a sent which is made of or coated with a radioactive material such as iridium 192. Since the radioactive material is provided on the outer surface of the sent, it is very difficult to precisely administer the proper dosage of radiation to prevent hyperplasia without administering a level of radiation which would actually induce hyperplasia or other deleterious effects to the blood vessel.
The Shefer PCT application illustrates a method and apparatus for restenosis treatment by applying a radioactive dose to the stenosed region after reduction of the region by angioplasty or other means. An angioplasty balloon is expanded in the vicinity of a lesion site and radioactive elements provided on the exterior surface of the balloon are forced into contact with the region. Therefore, similar to the Weinstein et al. patent, the presence of the radioactive material on the exterior of the catheter would make it very difficult to apply the precise amount of radiation to the region of interest. Additionally, both the Shefer PCT application and the Weinstein patent describe balloon catheters which do not allow the blood within the vessel to flow during inflation of the balloon.
Although there have been some attempts to construct a dilatation balloon allowing for some perfusion of bodily fluids during the inflation phase of the dilatation, the perfusion is greatly diminished by the overall size of the inflated balloon. Dilatation balloons must be able to hold a great amount of pressure (up to 16 atmospheres) and must also be able to inflate to large overall diameters to open the stenosis areas inside the bodily conduits or narrow tortuous passageways. Both of these requirements lead to large, bulky dilatation balloons that encompass most, if not all, of the area inside the stenosed vessel leading to large blockages of bodily fluids and thus allowing for little, if any perfusion.
Examples of these types of balloons are described in U.S. Pat. Nos. 5,295,959, issued to Gurbel et al and 5,308,356, issued to Blackshear, Jr. et al. Both of these patents describe a passive perfusion dilatation catheter having a series of non-longitudinal lobes. As particularly illustrated in the Blackshear, Jr. et al patent, virtually the entire interior of the bodily conduit is blocked when the dilatation balloon is inflated, thereby preventing the flow of bodily fluids around the treatment site. Additionally, due to the particular structure of the balloons utilized, neither the Gurbel et al. nor the Blackshear, Jr. et al. balloon can be used to precisely position the catheter within the bodily conduit at the site of treatment.
Attempts to utilize these types of dilatation balloons as a positioning balloon or treating the patient with radioactive materials would greatly compromise the patient during implementation of the treatment due to the diminished flow of bodily fluids or, in some cases, the complete blockage of bodily fluids. Any compromises to the dilatation balloon to achieve a greater flow rate would greatly decrease the effectiveness of the balloon on the stenosed area.
The present disclosure addresses the deficiencies of previous devices by treating the location of a stenosis in a blood vessel, or other hollow conduit or narrow tortuous passageway in the body by utilizing a dilatation balloon (or series of balloons) in conjunction with a stand-off balloon (or series of balloons), both of which are attached near distal end of a catheter. A radiopaque elongated, flexible guidewire is inserted into the body through a small incision and is then introduced into a blood vessel or similar conduit or passageway. Once in place, a catheter including the aforementioned dilatation balloon or balloons as well as one or more stand-off balloons would be maneuvered to the location of treatment.
The dilatation balloon or balloons is inflated and deflated one or more times to reduce the size of the stenosis. At this point, the stand-off balloon or balloons would be inflated. Since the stand-off balloons inflate symmetrically and are long with thin widths, they serve to position the treatment lumen of the catheter inside the prior stenosised area while allowing for maximum bodily perfusion. A radioactive source or sources is advanced into position through the treatment lumen of the catheter to the site of the original stenosis. With the stand-off balloon or balloons inflated, the catheter and the radioactive source or sources are correctly positioned within the bodily conduit or passageway to administer the precise dose to the original area of the stenosis. After a predetermined period of time has elapsed, the stand-off balloon or balloons are deflated and the radioactive source as well as the catheter and a guidewire are removed from the bodily conduit or passageway.
A normal angioplasty catheter including the catheter utilizing both dilatation as well as stand-off balloons are provided in a sterile ,package and is used entirely in a sterile environment to prevent contamination from being introduced into the patient""s body. The treatment channel or lumen of the aforementioned catheter is positioned within the catheter and contains an inner, closed channel. A radioactive source or sources is maneuvered from an afterloader through this channel until it nears the closed end to deliver therapy within the patient""s body.
The above-noted and other deficiencies of prior afterloaders are addressed by the present disclosure which is directed to a treatment catheter allowing a radioactive source or sources to be maneuvered from an afterloader in a non-sterile environment into a sterile environment without the occurrence of contamination. If a catheter employing both stand-off as well as dilatation balloons are placed into the patient""s body, it is important that the portion of the treatment lumen from the balloon inflation channel or channels to the distal end of the catheter provided within the patient""s body, must all be contained within a working sterile environment. It is noted that for purposes of explanation, the present disclosure is described with respect to a catheter employing both dilatation as well as stand-off balloons. However, as can be appreciated by practitioners in the medical art, it is not necessary to utilize this type of catheter to practice the teachings of the present disclosure.
It is not always possible to place a non-sterile radioactive source or sources into the treatment lumen of a catheter if the lumen is similar in length to the inflation lumen or lumens for inflating and discharging the dilatation or stand-off balloons without breaking the sterile field. Therefore, in order to maneuver this non-sterile radioactive source or sources through the treatment channel or lumen without breaking the sterile environment, a transport channel, or tube, protruding from the proximal end of the treatment channel of the catheter must be employed. This extra-long transport/treatment channel can be appreciably longer than the inflation lumen or lumens. This design allows an individual or an afterloading device located in an area outside the sterile field to maneuver the non-sterile source or sources through the treatment lumen to the treatment site, without breaking the surrounding sterile field.
There are two methods in which a radioactive source or sources can be loaded into the opening of the transport tube. One method is to physically load the source or sources by hand or by the use of forceps or other types of manipulators into the treatment channel. The second method is to load the source or sources by use of the remote afterloader. In order to accomplish this loading task, a specially designed hub provided on the proximal end of the transport tube must be utilized. This hub design contains a tapered or funnel opening to allow the radioactive source or sources to easily enter the proximal end of the transport tube of the catheter.
Therefore, the present disclosure features an extra long length treatment tube protruding from the proximal end of the catheter in conjunction with dilatation and/or stand-off balloons to allow a radioactive source or sources to be maneuvered from a non-sterile environment into the sterile environment of the patient""s body. The present disclosure further features a specially designed hub to assure the correct fit and connection of the treatment lumen to the afterloading device. This specially designed hub also directly communicates with the afterloading device after it is locked in place to insure that the connection between the treatment catheter and the afterloader is complete.